Repair of Asus RT-N16

Late last night, my router went down. Checking it, I saw that the lights were all off. Huh. So, I unplugged and replugged it, and it came back up. Figuring it was a glitch, I went back to bed, and thought nothing of it. This morning, I found it was off again, and re-plugging it would do nothing. Crap.

So, I pulled it off the wall, and opened it up. Hey look, a bad capacitor. It’s labeled as a 680uF 16V cap, with a nice bulged top. After finding a replacement in my capacitor stash, I went about removing the old one… which was, a pain. Mainly because it’s on a huge ground plane, so heating the leads enough to get it removed was a challenge. Even my FR-300 desoldering gun took a bit of work to get things hot enough to melt. But, after about 5 minutes of working on it, I got the old one out, and the new one in. The new one is a bit taller, but it does fit12.

Breaking out my LCR meter, I do see the bad cap shows only 160uF capacitance, and 0.8ohm of ESR. The new one shows 640uF capacitance (well within the 20% spec), and less than one tenth the ESR (0.03ohms). Pretty obvious from that why it popped (excessive ESR leads to heating due to power dissipation) I also took the opportunity to wash out the enclosure since it lives in my garage, and was full of dead spiders. Ugh. Putting it all back together, it powered right up.

Interestingly, after I’d done the work, and got things back up and running, I found this post by someone else that seems to show it’s a pretty common failure (given the comments, it looks like a fair number of these RT-N16’s must be aging out at this point).

And yes, I’m okay with a 16V capacitor in this case since the power supply is 12V (meaning a 75% derating) and the whole thing lives in my garage which is never above 20C. Yes, I know it’s above the minimum 70% derating, but not by much, and I didn’t have a 25V that would fit. [↩]

Also note: Asus, at least on this board, paints their capacitor markings backward. Where normally the negative capacitor lead would go in the solid white marked hole, it is actually the positive as can be seen for all the other caps on the board. Why Asus does this, I have NO idea. [↩]